The present invention relates to a semiconductor laser, a method of mounting a semiconductor laser, a semiconductor laser mounted structure, and an optical disk system, which are suitable for application to, for example, a semiconductor laser using a nitride type Group III-V compound semiconductor and an optical disk system using the semiconductor laser as a light source.
FIG. 8 shows a GaN based semiconductor laser using a GaN substrate according to the related art. As shown in FIG. 8, in this GaN based semiconductor laser, an n-type AlGaN clad layer 102, an n-type GaN light waveguide layer 103, an active layer 104 of an undoped Ga1-xInxN (well layer)/Ga1-yInyN (barrier layer, x>y) multiple quantum well structure, a p-type GaN light waveguide layer 105, a p-type GaN/AlGaN superlattice clad layer 106, and a p-type GaN contact layer 107 are sequentially laminated on an n-type GaN substrate 101. An upper portion of the p-type GaN/AlGaN superlattice clad layer 106 and the p-type GaN contact layer 107 are provided with a ridge 108 extending rectilinearly in one direction. An insulation layer 109 is formed to extend on the side surfaces of the ridge 108 and on those portions of the p-type GaN/AlGaN superlattice clad layer 106 which are located on the outside of the ridge 108. A p-side electrode 110 is formed on the ridge 108 in electrical contact with the p-type GaN contact layer 107. In addition, a pad electrode 111 is formed in electrical contact with the p-side electrode 110 so as to cover the p-side electrode 110 and the insulation layer 109. On the other hand, an n-side electrode 112 is formed in electrical contact with the back side of the n-type GaN substrate 101.
The semiconductor laser using a GaN substrate is disclosed, for example, in Japanese Patent Laid-open No. 2003-124572.
A method for mounting the above-mentioned GaN semiconductor laser will be described. As shown in FIG. 9A (top plan view), a solder 202 composed of Sn or an Sn mixed crystal metal such as AgSn and AuSn is formed in a stripe form on the upper surface of a rectangular sub-mount 201, a GaN based semiconductor laser chip 203 is so positioned that its ridge 108 is located on the stripe form solder 202, and a pressure is applied to the GaN based semiconductor laser chip 203 in the condition where the solder 202 is molten, thereby mounting the GaN based semiconductor laser chip 203 on the sub-mount 201. Then, as shown in FIG. 9B (a side view as viewed from a rear side end face), a stripe form bonding pad 204 formed on a peripheral portion of the sub-mount 201 and the n-side electrode 112 of the GaN based semiconductor laser chip 203 are bonded to each other by a wire 205. The sub-mount 201 is provided thereon with another stripe form bonding pad 206 in an area on the opposite side of the area where the bonding pad 204 is formed. Image recognition patterns 207 and 208 for use in positioning of the GaN based semiconductor laser chip 203 and the sub-mount 201 are provided respectively on two corner portions of the sub-mount 201.